Leone, A, Assessing Pre-Operative Cutting Modalities for Prosthetic Iris Devices

Introduction: For patients living with iris deficiencies, common symptoms including light sensitivity, glare, and shadow images (Figueiredo & Snyder, 2020) can be debilitating and hinder normal, everyday activities. Intraocular prosthetic iris devices, such as the CustomFlex® artificial iris, can provide some symptom relief, though inflammatory sequelae have been reported in some series, especially in which the device periphery was modified in the operating room, post-manufacture and pre-implantation (Mayer et al., 2019). Rough, sharp, and serrated edges of intraocular implants are known to cause inflammation, known as uveitis-glaucoma-hyphema (UGH) syndrome (Apple et al., 1984). Accordingly, a deeper dive into the microstructure of these new devices is warranted.

Methods: 7 pure silicone and 7 polyester fiber meshwork-embedded silicone CustomFlex® artificial iris devices were cut in clinically reported patterns by an experienced iris prosthesis surgeon (MES) mimicking surgical conditions. Both versions of the implant were similarly prepared and examined. The following devices were utilized for cutting: 1) large diameter round trephine blades from two manufacturers, 2) sharp ophthalmic “Vannas” micro scissors, and 3) straight-edged ophthalmic surgical blades. The following reported clinical patterns of cuts were created: 1) circumferential trephination alone, 2) edge trephination, creating scalloped “punch-outs,” 3) pseudoiridectomies, and 4) circumferential trimming with scissors. These sample devices were then coated with sputtered gold for analysis under a scanning electron microscope’s ETD detector, producing images that were later analyzed for rough or uneven edges.

Results: (Preliminary analysis) The cut edges of fiber-free implants were uniformly smoother than those of meshwork-embedded devices. Patterns other than concentric trephination created sharp corners and edge irregularities. All cutting patterns utilizing BVI® trephine blades produced the smoothest cut surfaces for both silicone-only and fiber meshwork-embedded implants. Tecfen® trephine blades produced rougher and more irregular cut surfaces for both silicone-only and, especially, fiber meshwork-embedded implants, in which the disturbance to the edge and meshwork were even grossly visible to the naked eye. Ophthalmic blades created reasonably smooth cuts in both versions of the device, with modest disruption of the meshwork fibers around the cut edge. Scissor cuts created intermediate irregularities in the fiber-free devices, but also displaced meshwork fibers farther than did cuts with a surgical blade in meshwork-embedded devices.

Conclusions: Sharp corners and irregular edges may explain the differing incidence of inflammation in reported cohorts of iris prosthesis patients. Cutting tools and patterns that minimize irregular edges or sharp corners that may contact uveal tissue may minimize UGH syndrome-related sequelae. Post-manufacture modification of these devices should ideally be limited to concentric trephination. Fiber-free devices should be chosen preferentially over meshwork-embedded versions, when clinically viable.